The present invention relates to an ultrasonic measuring apparatus for measuring the flow speed or flow rate of a fluid flowing through a measuring pipe by the use of an ultrasonic wave.
An ultrasonic fluid flow rate measuring apparatus of the type having a pair of electro-acoustical transducers disposed in respective up-stream and down-stream positions relative a fluid flow and the flow rate or flow speed is obtained from the difference between oscillation frequencies of first and second oscillation circuits are known in the art. For example, such an apparatus is disclosed in Japanese Patent Application (OPI) 130261/1974.
Such conventional apparatus, however, produces measuring errors due to the detected cycle in the received ultrasonic pulse being the preceding or following cycle and not the normal cycle.